Macrolenes dentipes

Notes on Macrolenes dentipes

The genus Macrolenes Chevrolat, 1836, includes the species Macrolenes dentipes (Olivier, 1808) and Macrolenes bellieri (Reiche, 1860); the latter recorded only in Sicily. M. dentipes is widely distributed in the Mediterranean region (Regalin & Medvedev 2010) and rather easily recognized for the male front legs having long and dentate femora (Fig. 14). The adults are observed on several plants [Pistacia, Rhus (Anacardiaceae), Quercus (Fagaceae), Fraxinus (Oleaceae), Paliurus and Ziziphus (Rhamnaceae)] from May to August, but they are preferably active leaf-eater on Pistacia lentiscus L. (Agoiz-Bustamante et al. 2019). Adults of M. dentipes are phytophagous, while larval stages are phyto-zoo-saprophagous (Schöller 1998). The females oviposit eggs in clusters attached to the leaf surface by long strands. The first instar larva is undescribed. Larval development occurs on the soil. The third larva, described by Medvedev & Schöller (2002) on specimens collected under a stone covering an ant’s nest under a Quercus ilex tree, is protected by a simple case, light grey to brownish, with the fine line-like structure on the surface. M. dentipes is one of the ant-nest beetles (Agrain et al. 2015), but according to Schöller & Witte (2007), the larvae of the most advanced genera of Clytrinae (Labidostomis and Macrolenes) have lost secondarily the ability to penetrate into the ant nests and remain at the entrance of the host’s nest, namely, a species of Tapinoma: a new, protected and food-rich niche of a dolichoderine.

In our study area a massive population of M. dentipes was recorded in May 2019. Adults were observed on several plants (Arbutus firstly unedo, Olea europaea, Pistacia lentiscus, Vitis vinifera), but they produced severe damages mostly on lentisk (Figs 12-13). Mating (Fig. 14) and egg clusters (Fig. 15) were observed mostly on olive tree leaves. Eggs (Fig. 16) are subcylindrical, basally pointed and distally trunked, 0.7-0.9 mm in length and 0.4 mm in width. The diameter of the egg distal end is about as that of the head of the first emerging larva of the leaf beetle (0.3 mm). The chorion of the egg is coated with brown material. The number of eggs/cluster varied from 4 to 38 (average: 18; SD ± 10.6, n = 23). The eggs hatched at the beginning of June (Fig. 17); after hatching, they showed the distal cap completely detached (Fig. 11). The first instar larva (Fig. 18), 0.8-0.9 mm in length, is typically J-shaped, with the last abdominal segments directed ventrally. The head chaetotaxy (Fig. 19) offers diagnostic characters for the identification of the species; in particular: the single seta, on each side of the epicranial suture, not simple but at least slightly spiny as the other dorsal epicranial setae, except the very long 3 rd seta; all frontal setae moderately or densely spiny, with the 3 rd pair not longer than the second one.In the key for the identification of the clytrine genera by Wasowska (2007), based on the first instar larva, the larva of M. dentipes runs near Lobidostomis, having one seta on each side of epicranial suture, on top of the head, but simple in the latter species, not spiny.